[PATCH v2] drm/scheduler: remove timeout work_struct from drm_sched_job

[Lucas Stach]

Hi Nayan,

Am Mittwoch, den 26.09.2018, 02:09 +0900 schrieb Nayan Deshmukh:
> having a delayed work item per job is redundant as we only need one
> per scheduler to track the time out the currently executing job.
> 
> v2: the first element of the ring mirror list is the currently
> executing job so we don't need a additional variable for it
> 
> Signed-off-by: Nayan Deshmukh <nayan26deshmukh at gmail.com>
> Suggested-by: Christian König <christian.koenig at amd.com>
> ---
>  drivers/gpu/drm/scheduler/sched_main.c | 31 ++++++++++++++++---------------
>  include/drm/gpu_scheduler.h            |  6 +++---
>  2 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 9ca741f3a0bc..4e8505d51795 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -197,19 +197,15 @@ static void drm_sched_job_finish(struct work_struct *work)
>  	 * manages to find this job as the next job in the list, the fence
>  	 * signaled check below will prevent the timeout to be restarted.
>  	 */
> -	cancel_delayed_work_sync(&s_job->work_tdr);
> +	cancel_delayed_work_sync(&sched->work_tdr);
>  
>  	spin_lock(&sched->job_list_lock);
> -	/* queue TDR for next job */
> -	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
> -	    !list_is_last(&s_job->node, &sched->ring_mirror_list)) {
> -		struct drm_sched_job *next = list_next_entry(s_job, node);
> -
> -		if (!dma_fence_is_signaled(&next->s_fence->finished))
> -			schedule_delayed_work(&next->work_tdr, sched->timeout);
> -	}
>  	/* remove job from ring_mirror_list */
>  	list_del(&s_job->node);
> +	/* queue TDR for next job */
> +	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
> +	    !list_empty(&sched->ring_mirror_list))
> +		schedule_delayed_work(&sched->work_tdr, sched->timeout);
>  	spin_unlock(&sched->job_list_lock);
>  
>  	dma_fence_put(&s_job->s_fence->finished);
> @@ -236,16 +232,21 @@ static void drm_sched_job_begin(struct drm_sched_job *s_job)
>  	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>  	    list_first_entry_or_null(&sched->ring_mirror_list,
>  				     struct drm_sched_job, node) == s_job)
> -		schedule_delayed_work(&s_job->work_tdr, sched->timeout);
> +		schedule_delayed_work(&sched->work_tdr, sched->timeout);
>  	spin_unlock(&sched->job_list_lock);
>  }
>  
>  static void drm_sched_job_timedout(struct work_struct *work)
>  {
> -	struct drm_sched_job *job = container_of(work, struct drm_sched_job,
> -						 work_tdr.work);
> +	struct drm_gpu_scheduler *sched;
> +	struct drm_sched_job *job;
> +
> +	sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);
> +	job = list_first_entry_or_null(&sched->ring_mirror_list,
> +				       struct drm_sched_job, node);
>  
> -	job->sched->ops->timedout_job(job);
> +	if (job)
> +		job->sched->ops->timedout_job(job);

I don't think this is fully robust. Jobs are only removed from the
ring_mirror_list once the job_finish worker has run. If execution of
this worker is delayed for any reason (though it's really unlikely for
a delay as long as the job timeout to happen) you are blaming the wrong
job here.

So I think what you need to to is find the first job in the ring mirror
list with an unsignaled finish fence to robustly find the stuck job.

Regards,
Lucas

>  }
>  
>  /**
> @@ -315,7 +316,7 @@ void drm_sched_job_recovery(struct drm_gpu_scheduler *sched)
>  	s_job = list_first_entry_or_null(&sched->ring_mirror_list,
>  					 struct drm_sched_job, node);
>  	if (s_job && sched->timeout != MAX_SCHEDULE_TIMEOUT)
> -		schedule_delayed_work(&s_job->work_tdr, sched->timeout);
> +		schedule_delayed_work(&sched->work_tdr, sched->timeout);
>  
>  	list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
>  		struct drm_sched_fence *s_fence = s_job->s_fence;
> @@ -384,7 +385,6 @@ int drm_sched_job_init(struct drm_sched_job *job,
>  
>  	INIT_WORK(&job->finish_work, drm_sched_job_finish);
>  	INIT_LIST_HEAD(&job->node);
> -	INIT_DELAYED_WORK(&job->work_tdr, drm_sched_job_timedout);
>  
>  	return 0;
>  }
> @@ -575,6 +575,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
>  	INIT_LIST_HEAD(&sched->ring_mirror_list);
>  	spin_lock_init(&sched->job_list_lock);
>  	atomic_set(&sched->hw_rq_count, 0);
> +	INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
>  	atomic_set(&sched->num_jobs, 0);
>  	atomic64_set(&sched->job_id_count, 0);
>  
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index daec50f887b3..d87b268f1781 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -175,8 +175,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>   *               finished to remove the job from the
>   *               @drm_gpu_scheduler.ring_mirror_list.
>   * @node: used to append this struct to the @drm_gpu_scheduler.ring_mirror_list.
> - * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the timeout
> - *            interval is over.
>   * @id: a unique id assigned to each job scheduled on the scheduler.
>   * @karma: increment on every hang caused by this job. If this exceeds the hang
>   *         limit of the scheduler then the job is marked guilty and will not
> @@ -195,7 +193,6 @@ struct drm_sched_job {
>  	struct dma_fence_cb		finish_cb;
>  	struct work_struct		finish_work;
>  	struct list_head		node;
> -	struct delayed_work		work_tdr;
>  	uint64_t			id;
>  	atomic_t			karma;
>  	enum drm_sched_priority		s_priority;
> @@ -259,6 +256,8 @@ struct drm_sched_backend_ops {
>   *                 finished.
>   * @hw_rq_count: the number of jobs currently in the hardware queue.
>   * @job_id_count: used to assign unique id to the each job.
> + * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
> + *            timeout interval is over.
>   * @thread: the kthread on which the scheduler which run.
>   * @ring_mirror_list: the list of jobs which are currently in the job queue.
>   * @job_list_lock: lock to protect the ring_mirror_list.
> @@ -278,6 +277,7 @@ struct drm_gpu_scheduler {
>  	wait_queue_head_t		job_scheduled;
>  	atomic_t			hw_rq_count;
>  	atomic64_t			job_id_count;
> +	struct delayed_work		work_tdr;
>  	struct task_struct		*thread;
>  	struct list_head		ring_mirror_list;
>  	spinlock_t			job_list_lock;